Melbus_Mitsubishi HU.ino

/* Melbus CDCHGR Emulator
 * Program that emulates the MELBUS communication from a CD-changer (CD-CHGR) in a Volvo V70 (HU-xxxx) to enable AUX-input through the 8-pin DIN-contact. 
 * This setup is using an Arduino Nano 5v clone
 * 
 * The HU enables the CD-CHGR in its source-menue after a successful initialization procedure is accomplished. 
 * The HU will remove the CD-CHGR everytime the car starts if it wont get an response from CD-CHGR (second init-procedure).
 * 
 * Karl Hagström 2015-11-04
 * mod by S. Zeller 2016-03-14
 * 
 * This project went realy smooth thanks to these sources: 
 * http://volvo.wot.lv/wiki/doku.php?id=melbus
 * https://github.com/festlv/screen-control/blob/master/Screen_control/melbus.cpp
 * http://forums.swedespeed.com/showthread.php?50450-VW-Phatbox-to-Volvo-Transplant-(How-To)&highlight=phatbox
 * 
 * pulse train width=120us (15us per clock cycle), high phase between two pulse trains is 540us-600us 
 */


#define SERDBG 1 
const uint8_t MELBUS_CLOCKBIT_INT = 1; //interrupt numer (INT1) on DDR3
const uint8_t MELBUS_CLOCKBIT = 3; //Pin D3 - CLK
const uint8_t MELBUS_DATA = 4; //Pin D4  - Data
const uint8_t MELBUS_BUSY = 5; //Pin D5  - Busy

volatile uint8_t melbus_ReceivedByte = 0;
volatile uint8_t melbus_CharBytes = 0;
volatile uint8_t melbus_OutByte = 0xFF;
volatile uint8_t melbus_LastReadByte[12] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
volatile uint8_t melbus_SendBuffer[9] = {0x00,0x02,0x00,0x01,0x80,0x01,0xC7,0x0A,0x02};
volatile uint8_t melbus_SendCnt=0;
volatile uint8_t melbus_DiscBuffer[6] = {0x00,0xFC,0xFF,0x4A,0xFC,0xFF};
volatile uint8_t melbus_DiscCnt=0;
volatile uint8_t melbus_Bitposition = 0x80;

volatile bool InitialSequence_ext = false;
volatile bool ByteIsRead = false;
volatile bool sending_byte = false;
volatile bool melbus_MasterRequested = false;
volatile bool melbus_MasterRequestAccepted = false;

volatile bool testbool = false;
volatile bool AllowInterruptRead = true;
volatile int incomingByte = 0;   // for incoming serial data

//Startup seequence
void setup() {
  //Data is deafult input high
  pinMode(MELBUS_DATA, INPUT_PULLUP);
  
  //Activate interrupt on clock pin (INT1, D3)
  attachInterrupt(MELBUS_CLOCKBIT_INT, MELBUS_CLOCK_INTERRUPT, FALLING); 
  //Set Clockpin-interrupt to input
  pinMode(MELBUS_CLOCKBIT, INPUT_PULLUP);
#ifdef SERDBG
  //Initiate serial communication to debug via serial-usb (arduino)
  Serial.begin(230400);
  Serial.println("Initiating contact with Melbus:");
#endif
  //Call function that tells HU that we want to register a new device
  melbus_Init_CDCHRG();
}

//Main loop
void loop() {
  //Waiting for the clock interrupt to trigger 8 times to read one byte before evaluating the data
#ifdef SERDBG
  if (ByteIsRead) {
    //Reset bool to enable reading of next byte
    ByteIsRead=false;




    if (incomingByte == ' ') {
    if(melbus_LastReadByte[11] == 0x0 && (melbus_LastReadByte[10] == 0x4A || melbus_LastReadByte[10] == 0x4C || melbus_LastReadByte[10] == 0x4E) && melbus_LastReadByte[9] == 0xEC && melbus_LastReadByte[8] == 0x57 && melbus_LastReadByte[7] == 0x57 && melbus_LastReadByte[6] == 0x49 && melbus_LastReadByte[5] == 0x52 && melbus_LastReadByte[4] == 0xAF && melbus_LastReadByte[3] == 0xE0 && melbus_LastReadByte[2] == 0x0)
    {
      melbus_CharBytes=8; //print RDS station name
    }

    if(melbus_LastReadByte[1] == 0x0 && melbus_LastReadByte[0] == 0x4A)
    {
      Serial.println("\n LCD is master: (no CD init)");
    }
    else if(melbus_LastReadByte[1] == 0x0 && melbus_LastReadByte[0] == 0x4C)
    {
      Serial.println("\n LCD is master: (???)");
    }
    else if(melbus_LastReadByte[1] == 0x0 && melbus_LastReadByte[0] == 0x4E)
    {
      Serial.println("\n LCD is master: (with CD init)");
    }
    else if(melbus_LastReadByte[1] == 0x80 && melbus_LastReadByte[0] == 0x4E)
    {
      Serial.println("\n ???");
    }
    else if(melbus_LastReadByte[1] == 0xE8 && melbus_LastReadByte[0] == 0x4E)
    {
      Serial.println("\n ???");
    }
    else if(melbus_LastReadByte[1] == 0xF9 && melbus_LastReadByte[0] == 0x49)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0x80 && melbus_LastReadByte[0] == 0x49)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0xE8 && melbus_LastReadByte[0] == 0x49)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0xE9 && melbus_LastReadByte[0] == 0x4B)
    {
      Serial.println("\n HU  is master: -> CDC");
    }
    else if(melbus_LastReadByte[1] == 0x81 && melbus_LastReadByte[0] == 0x4B)
    {
      Serial.println("\n HU  is master: -> CDP");
    }
    else if(melbus_LastReadByte[1] == 0xF9 && melbus_LastReadByte[0] == 0x4E)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0x50 && melbus_LastReadByte[0] == 0x4E)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0x50 && melbus_LastReadByte[0] == 0x4C)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0x50 && melbus_LastReadByte[0] == 0x4A)
    {
      Serial.println("\n HU  is master: ");
    }
    else if(melbus_LastReadByte[1] == 0xF8 && melbus_LastReadByte[0] == 0x4C)
    {
      Serial.println("\n HU  is master: ");
    }

    if (melbus_CharBytes) {
      Serial.write(melbus_LastReadByte[1]);
      melbus_CharBytes--;
    }else 
    {
      Serial.print(melbus_LastReadByte[1],HEX);
      Serial.write(' ');
    }
    }


  }
#endif



  //If BUSYPIN is HIGH => HU is in between transmissions
  if (digitalRead(MELBUS_BUSY)==HIGH) 
  {
    //Make sure we are in sync when reading the bits by resetting the clock reader

#ifdef SERDBG
    if (melbus_Bitposition != 0x80) {
      Serial.println(melbus_Bitposition,HEX);
      Serial.println("\n not in sync! ");
    }
#endif
  if (incomingByte != 'k') {
    melbus_Bitposition = 0x80;
    melbus_OutByte = 0xFF;
    melbus_SendCnt=0;
    melbus_DiscCnt=0;
    DDRD &= ~(1<<MELBUS_DATA);
    PORTD |= (1<<MELBUS_DATA);
  }

  }  
#ifdef SERDBG
  if (Serial.available() > 0) {
                // read the incoming byte:
                incomingByte = Serial.read();


  }
  if (incomingByte == 'i') {
                 melbus_Init_CDCHRG();
                 Serial.println("\n forced init: ");
                 incomingByte=0;

  }
#endif
  if ((melbus_Bitposition == 0x80) && (PIND & (1<<MELBUS_CLOCKBIT)))
  {
  delayMicroseconds(7);
  DDRD &= ~(1<<MELBUS_DATA);
  PORTD |= (1<<MELBUS_DATA);
  }

}

//Notify HU that we want to trigger the first initiate procedure to add a new device (CD-CHGR) by pulling BUSY line low for 1s
void melbus_Init_CDCHRG() {
  //Disabel interrupt on INT1 quicker then: detachInterrupt(MELBUS_CLOCKBIT_INT);
  EIMSK &= ~(1<<INT1); 
  
 // Wait untill Busy-line goes high (not busy) before we pull BUSY low to request init
  while(digitalRead(MELBUS_BUSY)==LOW){} 
  delayMicroseconds(10);
  
  pinMode(MELBUS_BUSY, OUTPUT);
  digitalWrite(MELBUS_BUSY, LOW);
  delay(1200);
  digitalWrite(MELBUS_BUSY, HIGH);
  pinMode(MELBUS_BUSY, INPUT_PULLUP);

  //Enable interrupt on INT1, quicker then: attachInterrupt(MELBUS_CLOCKBIT_INT, MELBUS_CLOCK_INTERRUPT, RISING);
  EIMSK |= (1<<INT1); 
}




//Global external interrupt that triggers when clock pin goes high after it has been low for a short time => time to read datapin
void MELBUS_CLOCK_INTERRUPT() {

    //Read status of Datapin and set status of current bit in recv_byte
      
      if(melbus_OutByte & melbus_Bitposition){
         DDRD &= (~(1<<MELBUS_DATA));
         PORTD |= (1<<MELBUS_DATA);
      }
      //if bit [i] is "0" - make databpin low
      else{
         PORTD &= (~(1<<MELBUS_DATA));
         DDRD |= (1<<MELBUS_DATA);
      }
      
 
     if (PIND & (1<<MELBUS_DATA)){
          melbus_ReceivedByte |= melbus_Bitposition; //set bit nr [melbus_Bitposition] to "1"
     }
     else {
          melbus_ReceivedByte &=~melbus_Bitposition; //set bit nr [melbus_Bitposition] to "0"
     }
    
  
    //if all the bits in the byte are read: 
    if (melbus_Bitposition==0x01) {
      
      //Move every lastreadbyte one step down the array to keep track of former bytes 
      for(int i=11;i>0;i--){
        melbus_LastReadByte[i] = melbus_LastReadByte[i-1];
      }

      if (melbus_OutByte != 0xFF) {
        melbus_LastReadByte[0] = melbus_OutByte;
        melbus_OutByte = 0xFF;
      } else {
      
         //Insert the newly read byte into first position of array
         melbus_LastReadByte[0] = melbus_ReceivedByte;
      }
      //set bool to true to evaluate the bytes in main loop
      ByteIsRead = true;

       
      //Reset bitcount to first bit in byte
      melbus_Bitposition=0x80;
    if(melbus_LastReadByte[2] == 0x07 && (melbus_LastReadByte[1] == 0x1A || melbus_LastReadByte[1] == 0x4A) && melbus_LastReadByte[0] == 0xEE)
    {
      InitialSequence_ext = true;
    }
    else if(melbus_LastReadByte[2] == 0x0 && (melbus_LastReadByte[1] == 0x1C || melbus_LastReadByte[1] == 0x4C) && melbus_LastReadByte[0] == 0xED)
    {
      InitialSequence_ext = true;
    }
    else if((melbus_LastReadByte[0] == 0xE8 || melbus_LastReadByte[0] == 0xE9) && InitialSequence_ext == true){
      InitialSequence_ext = false;

      //Returning the expected byte to the HU, to confirm that the CD-CHGR is present (0xEE)! see "ID Response"-table here http://volvo.wot.lv/wiki/doku.php?id=melbus
      melbus_OutByte = 0xEE;
    }
    else if((melbus_LastReadByte[2] == 0xE8 || melbus_LastReadByte[2] == 0xE9) && (melbus_LastReadByte[1] == 0x1E || melbus_LastReadByte[1] == 0x4E) && melbus_LastReadByte[0] == 0xEF)
    {
      // CartInfo
      melbus_DiscCnt=6;
    }
    else if((melbus_LastReadByte[2] == 0xE8 || melbus_LastReadByte[2] == 0xE9) && (melbus_LastReadByte[1] == 0x19 || melbus_LastReadByte[1] == 0x49) && melbus_LastReadByte[0] == 0x22)
    {
      // Powerdown
          melbus_OutByte = 0x00; // respond to powerdown;
          melbus_SendBuffer[1]=0x02; // STOP
          melbus_SendBuffer[8]=0x02; // STOP
    }
    else if((melbus_LastReadByte[2] == 0xE8 || melbus_LastReadByte[2] == 0xE9) && (melbus_LastReadByte[1] == 0x19 || melbus_LastReadByte[1] == 0x49) && melbus_LastReadByte[0] == 0x52)
    {
      // RND
    }
    else if((melbus_LastReadByte[2] == 0xE8 || melbus_LastReadByte[2] == 0xE9) && (melbus_LastReadByte[1] == 0x19 || melbus_LastReadByte[1] == 0x49) && melbus_LastReadByte[0] == 0x29)
    {
      // FF
    }
    else if((melbus_LastReadByte[2] == 0xE8 || melbus_LastReadByte[2] == 0xE9) && (melbus_LastReadByte[1] == 0x19 || melbus_LastReadByte[1] == 0x49) && melbus_LastReadByte[0] == 0x2F)
    {
      // FR
          melbus_OutByte = 0x00; // respond to start;
          melbus_SendBuffer[1]=0x08; // START
          melbus_SendBuffer[8]=0x08; // START
    }
    else if((melbus_LastReadByte[3] == 0xE8 || melbus_LastReadByte[3] == 0xE9) && (melbus_LastReadByte[2] == 0x1A || melbus_LastReadByte[2] == 0x4A) && melbus_LastReadByte[1] == 0x50 && melbus_LastReadByte[0] == 0x01)
    {
      // D-
          melbus_SendBuffer[3]--;
          melbus_SendBuffer[5]=0x01;
    }
    else if((melbus_LastReadByte[3] == 0xE8 || melbus_LastReadByte[3] == 0xE9) && (melbus_LastReadByte[2] == 0x1A || melbus_LastReadByte[2] == 0x4A) && melbus_LastReadByte[1] == 0x50 && melbus_LastReadByte[0] == 0x41)
    {
      // D+
          melbus_SendBuffer[3]++;
          melbus_SendBuffer[5]=0x01;
    }
    else if((melbus_LastReadByte[4] == 0xE8 || melbus_LastReadByte[4] == 0xE9) && (melbus_LastReadByte[3] == 0x1B || melbus_LastReadByte[3] == 0x4B) && melbus_LastReadByte[2] == 0x2D && melbus_LastReadByte[1] == 0x00 && melbus_LastReadByte[0] == 0x01)
    {
      // T-
          melbus_SendBuffer[5]--;
    }
    else if((melbus_LastReadByte[4] == 0xE8 || melbus_LastReadByte[4] == 0xE9) && (melbus_LastReadByte[3] == 0x1B || melbus_LastReadByte[3] == 0x4B) && melbus_LastReadByte[2] == 0x2D && melbus_LastReadByte[1] == 0x40 && melbus_LastReadByte[0] == 0x01)
    {
      // T+
          melbus_SendBuffer[5]++;
    }
    else if((melbus_LastReadByte[4] == 0xE8 || melbus_LastReadByte[4] == 0xE9) && (melbus_LastReadByte[3] == 0x1B || melbus_LastReadByte[3] == 0x4B) && melbus_LastReadByte[2] == 0xE0  && melbus_LastReadByte[1] == 0x01 && melbus_LastReadByte[0] == 0x08 ){
      // Playinfo
          melbus_SendCnt=9;
    }     
    if (melbus_SendCnt) {
         melbus_OutByte=melbus_SendBuffer[9-melbus_SendCnt];
         melbus_SendCnt--;
    } else if (melbus_DiscCnt) {
         melbus_OutByte=melbus_DiscBuffer[6-melbus_DiscCnt];
         melbus_DiscCnt--;
    }
    } else {
      //set bitnumber to address of next bit in byte
      melbus_Bitposition>>=1;
    }
    EIFR |= (1 << INTF1);
}

Hi,
I started sniffing text-exchange on the melbus, to implement on my car-pc project. checkout https://github.com/VincentGijsen/melbus-sniffed-traffic/blob/master/README.md for more details and captures on the bus

Hey,
I wanted to use this code in my Volvo S80 with a HU-801 Radio. The car RTI by default but I don't use it so I just disconnected it and connected my Arduino Uno (had it lying around) directly to the back of the radio. Thing is: It is not working. It's always telling me:
"40

not in sync!"
Sadly that doesn't really tell me anything about what is wrong. Could anyone help me out here, please?

@Jonatan-S
I expect your HU-801 is coded from the factory to expect a connection to the RTI unit. I don't know for sure, but I'd expect you'd have to flash the unit with the Volvo software to disable RTI.

Update: you may want to try plugging the RTI unit back in, and pulgging the UNO into the RTI. See here for more details

Hi, I just bought a volvo v70 2004 with a hu-803 and I would like to keep the head unit but I need the ability to play music from my own source via aux, usb or Bluetooth. I came across this project of yours which sounds great but I have spent a couple of weeks trying this myself with no luck. Initially with an arduino nano every, then a arduino mega then today with a regular nano clone. My first two attempts were with just jamming wires in the din plug at the back as a proof of concept but then I bought a din cable to splice to the arduino nano that I got for this which also had no luck. I have double checked the wiring connections (I also put a voltage regulator between run and vin for protection) but I haven't been able to make the cd changer appear. All that happens is a cd error message and then the internal cd player becomes unelectable. Not sure what to do from here, if anyone else has had a similar experience and has solved it and gotten it to work, please do let me know. I'll be trying again tomorrow to see